Automated precision manufacturing of titanium workpieces

10.12.2012

For the stable production of super-precise titanium welding tools, Herrmann Ultraschall relies on the combination of CNC 5 axis, high-performance machining centers with a robot-aided workpiece magazine and handling system supplied by Hermle.

Knowing how: In the course of 50 years, the intelligent implementation of physical laws has enabled the medium sized company Herrmann Ultraschall to advance to become a leading supplier and global player in the ultrasonic technology sector. In the Karlsbad headquarters alone, around 190 employees develop and produce machines, tools and complete solutions for the welding of thermoplastics or for cutting baked products.

Ultrasonic joining and cutting involves complex processes in which the joint types of the parts to be connected, the behavior of the materials, the shape and the physical vibration behavior of the sonotrodes have a decisive influence on the quality of the finished product. In this respect Herrmann Ultraschall leaves nothing to chance and sets great store by application consultation and know-how - in other words 'quality made in Germany': All components and assemblies are produced either in-house or by selected subcontractors.

The challenge

Especially the titanium sonotrodes require the absolutely highest degree of attention in respect of design, shaping, construction, programming and manufacturing. Plant manager Andreas Zipper: "For welding, the titanium sonotrode is made to vibrate. This involves the translation of electrical tension into ultrasound vibrations at frequencies between 20 and 35 kHz. The mechanical vibration of the sonotrode (35000 oscillations/sec at 35 kHz) is introduced into the fusion zone of the workpiece where it melts the material on account of molecular and interfacial friction, producing an exact, optically perfect and dense joint."

For reproducibly good welding results, extremely exactly manufactured titanium sonotrodes are essential. The prerequisite for this is a correspondingly high machining quality. For sonotrodes measuring 50 x 50 mm to 50 x 300 mm this means tolerances in the 40 μ range. Even tiny discrepancies have a negative effect on the welding quality. First, the basic shape must be created. This must then be tested in the welding system, possibly put back on the machine and adjusted for as long as is necessary until it is exactly right.

Simple, reliable, Hermle

In earlier days this represented a complex, multi-stage process. Now, Herrmann Ultraschall simply uses the Hermle C 30 U. "We have only been using 5 axis technology completely for a few years as yet," explains Andreas Zipper, "because it wasn't essential for many sonotrodes and we had several examples of partner companies making big promises that were followed by failed demonstrations. But an Open House at Hermle and then test processing of original materials quickly changed our minds: We

bought a C 30 U with NC swiveling rotary table (Ø 280 mm), an additional tool magazine with a total of 157 locations as well as zero-point pallet and workpiece clamping technology adapted to an RS 60 robot system. Hermle provided support for all project phases and the transition was successful. So the sonotrode production was successively transferred to the C 30 U. It fulfills all the requirements in respect of performance, precision, handling and reproducible quality."

Automating the production process

This confidence in the company and its machines led to further investments: two Hermle C 30 Us and an RS 2 robot system. In the course of the installation, the originally purchased C 30 U was upgraded and integrated into the system. This provided Herrmann Ultraschall with a complete manufacturing system from a single supplier. It is in operation round the clock to produce high-quality titanium sonotrodes requiring long processing times (up to 12 hours). Especially during the unmanned night shift and at weekends, work can carry on without interruption.

Typical Hermle reliability

Andreas Zipper comments: "To produce the current quantities of 5000 to 6000 sonotrodes per year using titanium with its problematical machining characteristics, it is most important to be able to rely fully on human and machine performance. With the Hermle hardware we have the capacity and quality prerequisites that we need to be able to cope with these quantities and this complexity reliably and in multi-shift operation. At first the workforce was concerned about job risks, but through information, training and higher qualification we were able to show that precisely in order to keep the jobs, the way forward was in automating the production. And our success proves it: The next investments in Hermle systems are already being planned."